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The Downside to Dedicated Lines vs. the Benefits

From an AC power grunge perspective, my main system currently seems very quiet. That is, I don’t have any ground hum issues, and I have to raise the gain fairly high and then get my ear quite close to one of the speakers before I can detect any hiss or other noise. It is truly the quietest system I’ve ever had experience with. Never the less, I do know that paying attention to AC power issues can reap other benefits, including an improved soundstage, imaging, better dynamics, etc.

I built this system from the ground up about a year ago and am now at the phase where I’m beginning to work on optimizing it. Back when I started planning it out, there was no question that I would be putting in a couple of dedicated lines. However, now that I’m at the point where I’m about to begin the project, and after a ton of reading and research, I’ve begun to have some serious reservations.

My concerns are mainly over the potential for introducing (or increasing) ground or ground-loop noise and/or hum. From what I can gather, powering interconnected components (especially non-balanced, or single ended, components) from multiple circuits, whether dedicated or not, raises the risk of this occurring.

I also understand the type of components as well as the system’s overall configuration plays a part as well. If I could summarize the details of my system and get some opinions about whether I run the risk of messing with an already good thing, I’d be very grateful.

The majority of my gear sits in a metal rack (Middle Atlantic) in an enclosure located directly behind the front wall of my listening room. XLR cables feed through the wall to a couple of mono amps that sit in the listening room near the speakers. The system currently doubles as a HT and 2ch rig and, as with most folks here, will no-doubt evolve and experience its share of equipment changes. As such, there’s a good chance I may not have a fully balanced system at any given point in time.

Right now, all of the audio gear, a cable box, an active sub, and a 60” plasma TV run off of one 20 amp circuit. There are various other wall-wart devices using the circuit as well (computer switch, rack fan, the receiver for my RF remote control, etc.) There might be a couple of incandescent lights that run on it too, but no other devices or equipment.

Everything currently runs through a couple of top-of-the line Belkin ‘Pure Power’ UPS/Surge Suppress/Conditioning units. Plans always were to repurpose these units after the dedicated lines were installed. However, considering the virtual lack of AC grunge despite all that’s plugged into them, I’m amazed at what these units are capable of.

If I do go ahead with installing the dedicated lines, I would put in a 100 amp sub-panel in the room that houses the rack. I’d need to pull about 80 feet of wire back to the main panel. (BTW, I don’t know much about the electrical trade, so if someone could offer guidance on what type of cable and gauge I should run, I’d appreciate it.) I’d then run 10/2 cryo’d romex (just because) out to three or four audiophile grade duplex outlets. Unfortunately, with where I’d be putting the sub panel, an isolation transformer wouldn’t be practical.

I would like to keep the existing branch circuit in place, and plug all the non-audio gear into it via the existing Belkin units (wall warts, cable box, TV, etc.) The front end equipment, sources, sub, and amps would go on the dedicated lines… directly at first…but eventually I’m sure I’ll end up trying one or two of the better power conditioners that are often sold here on Audiogon.

Now…from all that I’ve read, it appears that the above configuration could be prone to ground noise/hum issues. If I’ve correctly understood a publication that Middle Atlantic has out, a large part this potential comes from the fact that the metal rack serves to interconnect all the components stored in it.

What I’m concerned about is this. Since these interconnected components will be plugged into different circuits…i.e., a branch circuit that terminates at a panel 80 feet away, while the rest will use dedicated circuits that terminate a few feet away at the sub panel….will I end up with ground loop noise issues? As I said, the system is already very quiet and I would hate to lose more than I would gain.

Is there any wiring strategy that might help avoid it? I’m not sure I exactly understand the concept, but if I told my electrician to ‘star ground’ the dedicated lines, would that be enough? Should I instead think about putting the subpanel closer to the main panel? On the other hand, would it be better to not risk it and instead invest in one of the uber-top of the line power conditioners, or perhaps a power regenerator?

Whatever opinions or advice I can get from the Audiogon community would be appreciated.
shutterman
shutterman OP
7 posts
 
"You may run into a ground loop hum. If you do purchase a www.jensen-transformers.com/ isolator. I had hum from a powered subwoofer and the cable tv cable"

Thanks...appreciate the link. I knew there were other humbusters out there, but I just didn't think about Jensen. My impression is they make some quality stuff, so this will be a nice link to hang on to. However, I'm hoping to find a way to do the dedicated lines and end up not having the need for something like this.
inline_phil
11 posts
 
You are correct in your concerns. Improper grounding creates ground loops not only internally to the circuit but also from component to component. Fortunately today, most high end equipment manufacturers have learned what the medical industry has known since the introduction of electronic scalpels in the 1960s.

A ground loop is any grounding scheme that can take more than one path to reach earth. So if your preamp and power amp both use a 3-wire grounded plug and you plug them into different electrical circuits and then you ground them to each other with your interconnect cables, you have by definition a ground loop.

The more components you connect in this fashion, the more ground loops you create. For this reason, it is best to use one lare circuit to feed your system rather than several smaller ones. If you use a line conditioner - as you should - buy one that will handle all of your equipment and run a dedicated line to that. Then plug everything into it.

Now this assumes that the transformers inside each piece of equipment have been properly tested and wired for lowest line leakage (properly phased) upon assembly by the manufacturer. Easy to check. Unplug everything from the component and lift the ground wire from that component by using what's called a "cheater" plug. Plug the cheater into the wall outlet and measure the voltage from the ground wire to earth ground inside the wall outlet. Then reverse the polarity of the cheater plug in the wall outlet and measure this voltage again. If the voltage lowers in the reverse direction, the power transformer phase inside that component is wired improperly and should be reversed. Do this for each component and all will be well in OZ.

Even those components using two-wire plugs can have this phasing problem. A similar scenario can be used to test ground leakage voltage by measureing from a circuit ground of the component to the wall outlet (use a ground pin on the component or the shield of an RCA plug).

Balanced component systems have an advantage over single-ended (RCA style) systems here in that they use additional electronic wizardry (called the common mode rejection ratio) to again lower the influences of ground loops and other stray electrical influences imposed on the interconnect cables.
shutterman OP
7 posts
 
"I'm not aware of any "downside" to using dedicated lines.
I do, however, suggest installing two lines -- not much more trouble really -- and then you can separate components as you wish - i.e: front end/amps, digital/analog, motors/electronics, etc."

Well...the downside is the increased potential for ground hum or noise as stated in my post, so I'm not sure I fully understand what you mean. Are you saying that you don't believe such potential exists? If so, I'd certainly like to believe you are correct. However, based on posts from the archives here and on articles posted other places, I came away with the impression that the potiential increases in configurations as the one I cited above.

Regarding the recommendation for two lines...yes, as I stated, plans are for at least two. I would have to have at least two as the amps are in one room while the rest of the equipment is in another.
shutterman OP
7 posts
 
"The more components you connect in this fashion, the more ground loops you create. For this reason, it is best to use one lare circuit to feed your system rather than several smaller ones. If you use a line conditioner - as you should - buy one that will handle all of your equipment and run a dedicated line to that. Then plug everything into it."

This is certainly the impression I too have come away with in my readings. This is probably why I don't have any ground hum issues with my current setup. While it is not a dedicated line per se, all the equipment IS plugged into one circuit.

Your comments and the link Danielk provided to BAT Technologies FAQ page (thanks, Danielk!) have started me thinking that using one line to feed everything might be the best solution in my case...especially since the metal equipment rack interconnects a good portion of the gear.

However, my difficulty in doing this is that I have the mono amps in one room, and the rest of the equipment in another.
dlcockrum's avatar
dlcockrum
2,190 posts
 
Two factors to consider:

1) Done properly, it is good to run analog and digital components on different lines on the same phase of the fuse box.

2) How much current does your amp(s) draw? If it is a high power model, it will benefit from having its own 20 amp line.

If you want to isolate your analog equipment from the digital (without a power conditioner) and your amp really needs its own dedicated 20 amp line, then you will need 3 lines!

I have not used the Belkin units but I strongly suspect that you will find after installing dedicated lines that your system will sound best without them (it probably will sound better without them now).

If surges are your concern, then use the blue whole house unit that has been recommended numerous times on Audio Asylum.

If you must use a power conditioner (don't just assume that you do), you are right to only consider the SOTA: Synergistic Research Powercell 10SE, Audience aR6-T, etc. You would want to run all of your components through these for maximum benefit (only need one "strong" 20 amp line).

Running two lines is indeed not significantly more expensive that running one as others have said. If it works out the your system works better through a single line, you really haven't lost much money.

The trick to eliminate ground loops is to run all of the lines powering your equipment to the same phase (leg) of ground in your fuse box. It is also a good idea to isolate all of the "noisy" lines on the other phase from your equipment. Your electrician should understand this readily.

Minimizing ground leakage as perfectly described by Inline phil is also a worthwhile exercise.
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